Metronidazole tablet and preparation method thereof

Abstract

The invention relates to the technical field of pharmaceutical preparations, and particularly discloses a metronidazole tablet and a preparation method thereof. The preparation method comprises the following steps: micronizing metronidazole to obtain pretreated metronidazole; mixing the pretreated metronidazole, corn starch, cane sugar, carboxymethyl starch sodium and an adhesive, granulating, drying, and finishing to obtain a core material; and mixing the core material, carboxymethyl starch sodium and magnesium stearate, and tabletting to obtain the metronidazole tablet. The micronization treatment comprehensively improves the physical and chemical properties of metronidazole by regulating and controlling the particle size, form and crystal form. The carboxymethyl starch sodium has a relatively high expansion rate, and can cooperate with particle pores formed by the adhesive by adopting a specific internal and external addition mode, so that the dissolution rate is improved; the cane sugar assists in dissolving, so that the dissolution peak reaching time is shortened, and the medicine takes effect quickly; the corn starch and the adhesive enhance the compressibility of the particles, and the magnesium stearate controls the amount and prevents sticking, so that the formability is improved, and the loss is reduced.

Description

Technical Field

[0001] This invention relates to the field of pharmaceutical preparation technology, and in particular to a metronidazole tablet and its preparation method. Background Technology

[0002] Metronidazole, chemically known as 2-methyl-5-nitroimidazole-1-ethanol, is a commonly used nitroimidazole antibiotic in clinical practice. It exerts its antibacterial effect by inhibiting bacterial DNA synthesis and is highly active against anaerobic bacteria (such as Bacteroides fragilis and Fusobacterium), Trichomonas vaginalis, and amoebae. It is widely used to treat diseases such as abdominal infections, pelvic infections, oral anaerobic bacterial infections, and trichomonal vaginitis. It has a large clinical demand and a wide range of applications.

[0003] As an oral solid dosage form, the preparation process of metronidazole tablets directly determines its quality attributes (such as content uniformity, dissolution, and related substances) and clinical efficacy. In the existing technology, the mainstream preparation methods of metronidazole tablets mainly include wet granulation and tableting, dry granulation and tableting, and direct powder compression. However, due to the physicochemical properties of metronidazole itself (slightly soluble in water, with a solubility of only about 1 g / L at 25°C; melting point of 159°C~163°C, sensitive to damp heat and light; poor powder compressibility and large angle of repose), the above processes generally have technical defects and it is difficult to balance drug quality, production efficiency, and industrial feasibility. Wet granulation and tableting is the mainstream preparation process for metronidazole tablets. This process has the following core problems: Metronidazole is prone to degradation under humid and hot environments, generating substances such as 2-methyl-5-nitroimidazole, resulting in a high risk of drug degradation and directly affecting medication safety; Metronidazole is only slightly soluble in water, and its dissolution rate depends on the interface between particle disintegration and drug dissolution, leading to unstable dissolution; Batch-process operation requires multiple material transfers during drying and granulation, resulting in a long production cycle and prolonged exposure of materials to air, easily introducing cross-contamination risks; Simultaneously, the manual control of particle uniformity leads to large differences in particle size distribution, with tablet weight variation often exceeding ±5%. Furthermore, metronidazole is sensitive to light and humidity, causing the drug to absorb moisture and undergo photodegradation during preparation, resulting in poor stability; the binder polyvinylpyrrolidone (PVP K30) may undergo a cross-linking reaction with metronidazole under high-temperature environments (such as the wet granulation and drying process), forming insoluble complexes and reducing dissolution.

[0004] In summary, existing methods for preparing metronidazole tablets are limited by the drug's physicochemical properties and insufficient process adaptability, generally suffering from technical problems such as excessive levels of related substances, unstable dissolution, poor content uniformity, low production efficiency, and poor stability. These methods fail to simultaneously meet pharmacopoeia quality standards, clinical drug needs, and industrial production requirements. Therefore, developing a method for preparing metronidazole tablets that effectively addresses these shortcomings and achieves high quality, high efficiency, and low cost has become an urgent technical challenge in this field. Summary of the Invention To address the above problems, this invention provides a metronidazole tablet and its preparation method. By precisely designing the excipients and combining them with a specific preparation process, the uniformity of the content of the active pharmaceutical ingredient metronidazole is improved, as well as the dissolution and stability of metronidazole.

[0005] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows: In a first aspect, the present invention provides a method for preparing metronidazole tablets, comprising the following steps: S1. Metronidazole is micronized to obtain pretreated metronidazole; S2. The pretreated metronidazole, corn starch, sucrose, sodium carboxymethyl starch and binder are mixed, granulated, dried and sized to obtain the core material; S3. Mix the core material, sodium carboxymethyl starch and magnesium stearate, compress the mixture into tablets, and obtain metronidazole tablets. The amount of sodium carboxymethyl starch used in S2 is lower than that used in S3.

[0006] Compared to existing technologies, the metronidazole tablet preparation method provided by this invention utilizes micronization to comprehensively improve the physicochemical properties of metronidazole by controlling particle size, morphology, and crystal form. After micronization, the particle size of metronidazole is reduced to D50 = 5μm~10μm, and the specific surface area increases, greatly improving the contact interface between the drug and the dissolution medium, thus enhancing solubility and laying the foundation for rapid tablet dissolution. The pretreated metronidazole is predominantly spherical with a reduced angle of repose, effectively solving the problems of uneven material mixing and large tablet weight differences during compression in wet granulation. Micronization reduces residual crystalline impurities in the raw materials, improves the purity of the main crystal form, reduces the degradation rate under humid and hot conditions, and decreases the formation of related substances. Combined with other internal and external excipients, it can further extend the shelf life of the tablets.

[0007] This invention systematically optimizes the existing wet granulation process for metronidazole tablets by precisely designing the raw material composition, addressing key pain points such as high drug degradation risk, unstable dissolution, and poor tablet formability. The metronidazole tablets use sodium carboxymethyl starch as a disintegrant, corn starch and sucrose as fillers, and magnesium stearate as a lubricant. Sodium carboxymethyl starch has a high expansion rate and, through a specific internal and external addition method, can synergistically work with the pores formed by the binder, achieving a dissolution rate of 88%~96% within 30 minutes. Sucrose aids dissolution, shortening the time to peak dissolution and ensuring rapid drug onset of action. Corn starch and the binder enhance the compressibility of the granules, while magnesium stearate, through controlled dosage, prevents sticking and improves formability, reducing losses.

[0008] Preferably, the metronidazole tablets comprise the following raw materials in parts by weight: 100 parts metronidazole, 15 to 25 parts corn starch, 12 to 18 parts sucrose, 10 to 15 parts sodium carboxymethyl starch, 25 to 35 parts binder, and 1 to 2 parts magnesium stearate.

[0009] More preferably, the metronidazole tablets comprise the following raw materials in parts by weight: 100 parts metronidazole, 18 to 22 parts corn starch, 14 to 16 parts sucrose, 11 to 14 parts sodium carboxymethyl starch, 28 to 32 parts binder, and 1.2 to 1.8 parts magnesium stearate.

[0010] Preferably, in S1, the micronization process includes spray drying or air jet milling (more preferably spray drying).

[0011] More preferably, in S1, during the spray drying process, the metronidazole is prepared into a 15wt%~20wt% metronidazole solution using an alcohol solvent.

[0012] The preferred metronidazole solution concentration of this invention can increase production without clogging the nozzle.

[0013] More preferably, in S1, the alcohol solvent in the spray drying process comprises ethanol and water in a volume ratio of (1.2~1.8):1.

[0014] More preferably, in S1, the feed rate of the spray dryer is 8 mL / min to 12 mL / min, the atomizing pressure is 0.25 MPa to 0.35 MPa, the inlet air temperature is 110℃ to 120℃, and the outlet air temperature is 55℃ to 65℃.

[0015] This invention, by limiting the conditions of spray drying, further ensures the performance of pretreated metronidazole and is more suitable for the subsequent wet granulation process. The feed rate ensures that the droplets are fully dried in the drying tower; the atomizing air pressure disperses the liquid into droplets of appropriate size (droplets that are too large will result in insufficient drying, while droplets that are too small will easily lead to excessively fine particles and agglomeration); the inlet and outlet air temperatures can respectively prevent drug melting and drug degradation.

[0016] For example, each auxiliary material needs to be sieved before application. Corn starch, sodium carboxymethyl starch, and stearic acid are sieved through a 100-mesh sieve, while sucrose is pulverized in a high-efficiency pulverizer equipped with an 80-mesh stainless steel sieve.

[0017] Preferably, in step S2, the method for preparing the adhesive includes the following steps: Corn starch and ethanol are mixed, and water at 80℃~100℃ is added. The mixture is stirred until homogeneous to obtain the adhesive.

[0018] The metronidazole tablets of this invention use a starch paste based on a starch-ethanol-water system as a binder. Ethanol reduces water introduction, shortens drying time, and inhibits the hydrothermal degradation of metronidazole, thereby reducing drug degradation and improving safety. Using warm water at a specific temperature to prepare the binder better meets the wet granulation requirements of metronidazole tablets. Warm water promotes full gelatinization of corn starch, causing corn starch granules to absorb water, swell, and rupture, forming a uniform and viscous colloidal system. The adhesive strength is 30%–50% higher than that prepared with cold water, ensuring stable granule formation during granulation and preventing loose tablets. Simultaneously, controlling the water temperature shortens gelatinization time, improves the uniformity of the gelatinized system, avoids uneven granule hardness caused by ungelatinized starch, and ensures consistent tablet dissolution. A moderately high temperature (80°C–100°C) reduces the total water consumption of the binder. Combined with the volatility of ethanol, this further reduces the hydrothermal exposure of metronidazole during wet granulation, reducing the formation of related substances. Furthermore, the specific temperature of warm water prevents excessive ethanol evaporation at high temperatures while maintaining the fluidity of the paste.

[0019] More preferably, in S2, the mass ratio of corn starch, ethanol and water in the adhesive is 1:(5.5~6.5):(2.5~3.5).

[0020] By controlling the amount of each raw material, this invention can further enhance the synergistic effect of each raw material, thereby further improving the dissolution performance and stability of metronidazole.

[0021] More preferably, in S2, the temperature at which the water is added is 90℃~100℃.

[0022] This invention, by controlling the temperature at which water is added, facilitates the full gelatinization of corn starch while ensuring that the mixing temperature is within an appropriate range (≤75℃, so that ethanol will not evaporate).

[0023] For example, in S2, the mixing time is 15 min to 35 min.

[0024] In example, in S2, granulation is carried out in a gyratory pellet mill using an 18-mesh nylon screen.

[0025] Preferably, in step S2, the drying temperature is 45℃~55℃ and the drying time is 25min~35min.

[0026] For example, in S2, granulation is carried out in a gyratory pellet mill using a 16-20 mesh nylon screen.

[0027] Preferably, the mass ratio of sodium carboxymethyl starch in S2 to sodium carboxymethyl starch in S3 is 1:(1.2~2).

[0028] For example, in S3, the mixing is carried out in a three-dimensional motion mixer for 25 to 35 minutes.

[0029] For example, in S3, a rotary tablet press is used for tableting, and the speed of the tablet press is 15 rpm to 18 rpm.

[0030] Secondly, the present invention provides a metronidazole tablet prepared by the aforementioned method for preparing metronidazole tablets.

[0031] The present invention has the following beneficial effects: In existing wet granulation processes for metronidazole tablets, traditional water-based adhesives introduce a large amount of moisture, and the drying process requires high-temperature, long-term treatment. This can easily lead to the degradation of metronidazole in a humid and hot environment, generating related substances such as 2-methyl-5-nitroimidazole, posing a risk of exceeding the limits for these substances. This invention employs a "starch-ethanol-water" composite solvent system. The introduction of ethanol significantly reduces the overall water content of the adhesive, minimizing the contact between metronidazole and water during granulation. Simultaneously, the volatile nature of ethanol shortens the subsequent drying time, and the drying temperature is correspondingly lowered, preventing metronidazole degradation due to prolonged high-temperature exposure.

[0032] The synergistic effect of a specific ratio of corn starch and sucrose forms a loose and porous granular skeleton during granulation, reducing the aggregation of metronidazole particles and further lowering the local concentration of the drug in a humid and hot environment, thus preventing the chain reaction of degradation reactions. A specific amount of sodium carboxymethyl starch is selected as the disintegrant, which has a high water absorption and swelling rate. Through a combination of internal and external addition, it can exert a swelling effect both inside and outside the core material during tablet disintegration, rapidly destroying the particle structure. Simultaneously, the volatility of ethanol in the binder can form micropores inside the particles, increasing the contact area between metronidazole and the dissolution medium. The synergistic effect of these two factors ensures that the dissolution rate of the metronidazole tablets of this invention remains stable at 88%~95% within 30 minutes, with a smooth dissolution curve (RSD≤3%), ensuring stable and compliant drug concentrations after clinical administration. Furthermore, the internal excipients contain no metal ions and will not undergo complexation reactions with metronidazole, further inhibiting the formation of related substances.

[0033] The excipients used in this invention are common and low in cost, the preparation method is simple and easy to implement, it is compatible with existing wet granulation lines, does not require large-scale equipment modification, is suitable for mass production, and has good market applicability. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0035] In this embodiment of the invention, the water is purified water; the corn starch was purchased from Henan Zhenghong Pharmaceutical Excipients Co., Ltd.; the sucrose was purchased from Baoding Tianlong Sugar Industry Co., Ltd.; sodium hydroxymethyl starch was purchased from Yongri Chemical Industry Co., Ltd., Taichung Young Lion Plant, Type A; and magnesium stearate was purchased from Huzhou Zhanwang Pharmaceutical Co., Ltd., Type ZW-MS-8. The model of the oscillating granulator is YK-160, the model of the three-dimensional motion mixer is SYH-1000, and the model of the rotary tablet press can be ZP35B or ZP-35D. All other materials unless otherwise specified are commercially available products.

[0036] Example 1 This embodiment provides a method for preparing metronidazole tablets, including the following steps: S100. Mix corn starch and pharmaceutical ethanol evenly, add water at 95°C, the mass ratio of corn starch, pharmaceutical ethanol and water is 1:6:3, stir evenly to obtain adhesive.

[0037] 100 parts of metronidazole were added to an alcohol solvent (a mixture of pharmaceutical ethanol and water in a volume ratio of 1.5:1) to prepare an 18wt% metronidazole solution, which was then spray-dried (feed rate of 10mL / min, atomization pressure of 0.3MPa, inlet air temperature of 110℃, and outlet air temperature of 60℃) to obtain pretreated metronidazole.

[0038] S200: Add pretreated metronidazole, 20 parts corn starch, 15 parts sucrose and 5 parts sodium carboxymethyl starch to a high-speed mixing granulator. Mix for 20 minutes, then add 30 parts binder and continue mixing for 15 minutes. Transfer to a gyratory pellet mill (18-mesh nylon screen) for granulation. Dry at 50°C for 30 minutes. Granulate in a gyratory pellet mill (18-mesh nylon screen) to obtain core material.

[0039] S300: Add the core material, 7.5 parts sodium carboxymethyl starch and 1.5 parts magnesium stearate to a three-dimensional motion mixer, mix for 30 minutes, and then compress the mixture into tablets using a rotary tablet press (the speed of the tablet press is 16 rpm) to obtain metronidazole tablets.

[0040] The metronidazole tablets prepared in this embodiment comprise the following raw materials in parts by weight: 100 parts metronidazole, 20 parts corn starch, 15 parts sucrose, 12.5 parts sodium carboxymethyl starch (5 parts + 7.5 parts), 30 parts binder, and 1.5 parts magnesium stearate. The mass ratio of sodium carboxymethyl starch in S200 to sodium carboxymethyl starch in S300 is 1:1.5.

[0041] Example 2 This embodiment provides a method for preparing metronidazole tablets, including the following steps: S100 is the same as in Example 1, and will not be described again.

[0042] S200: Add pretreated metronidazole, 22 parts corn starch, 14 parts sucrose and 5 parts sodium carboxymethyl starch to a high-speed mixing granulator. Mix for 20 minutes, then add 33 parts binder and continue mixing for 15 minutes. Transfer to a gyratory pellet mill (18-mesh nylon screen) for granulation. Dry at 50°C for 30 minutes. Granulate in a gyratory pellet mill (18-mesh nylon screen) to obtain core material.

[0043] S300: Add the core material, 7 parts sodium carboxymethyl starch and 1.3 parts magnesium stearate to a three-dimensional motion mixer, mix for 30 minutes, and then compress the mixture into tablets using a rotary tablet press (the speed of the tablet press is 16 rpm) to obtain metronidazole tablets.

[0044] The metronidazole tablets prepared in this embodiment comprise the following raw materials in parts by weight: 100 parts metronidazole, 22 parts corn starch, 14 parts sucrose, 12 parts sodium carboxymethyl starch (5 parts + 7 parts), 33 parts binder, and 1.3 parts magnesium stearate. The mass ratio of sodium carboxymethyl starch in S200 to sodium carboxymethyl starch in S300 is 1:1.4.

[0045] Example 3 This embodiment provides a method for preparing metronidazole tablets, including the following steps: S100. Mix corn starch and pharmaceutical ethanol evenly, add water at 100°C, the mass ratio of corn starch, pharmaceutical ethanol and water is 1:6.5:2.5, stir evenly to obtain adhesive.

[0046] 100 parts of metronidazole were added to an alcohol solvent (a mixture of pharmaceutical ethanol and water in a volume ratio of 1.3:1) to prepare a 20 wt% metronidazole solution, which was then spray-dried (feed rate of 8 mL / min, atomization pressure of 0.35 MPa, inlet air temperature of 110℃, and outlet air temperature of 55℃) to obtain pretreated metronidazole.

[0047] S200: Add pretreated metronidazole, 22 parts corn starch, 16 parts sucrose and 5.5 parts sodium carboxymethyl starch to a high-speed mixing granulator. Mix for 20 minutes, then add 32 parts binder and continue mixing for 15 minutes. Transfer to a gyratory pellet mill (18-mesh nylon screen) for granulation. Dry at 55°C for 25 minutes. Granulate in a gyratory pellet mill (20-mesh nylon screen) to obtain the core material.

[0048] S300: Add the core material, 8.5 parts of sodium carboxymethyl starch and 1.8 parts of magnesium stearate to a three-dimensional motion mixer, mix for 25 minutes, and then compress the mixture into tablets using a rotary tablet press (the speed of the tablet press is 18 rpm) to obtain metronidazole tablets.

[0049] The metronidazole tablets prepared in this embodiment comprise the following raw materials in parts by weight: 100 parts metronidazole, 22 parts corn starch, 16 parts sucrose, 14 parts sodium carboxymethyl starch (5.5 parts + 8.5 parts), 32 parts binder, and 1.8 parts magnesium stearate. The mass ratio of sodium carboxymethyl starch in S200 to sodium carboxymethyl starch in S300 is 1:1.55.

[0050] Example 4 This embodiment provides a method for preparing metronidazole tablets, including the following steps: S100. Mix corn starch and pharmaceutical ethanol evenly, add water at 90°C, the mass ratio of corn starch, pharmaceutical ethanol and water is 1:5.5:3.5, stir evenly to obtain adhesive.

[0051] 100 parts of metronidazole were added to an alcohol solvent (a mixture of pharmaceutical ethanol and water in a volume ratio of 1.7:1) to prepare a 15 wt% metronidazole solution, which was then spray-dried (feed rate of 12 mL / min, atomization pressure of 0.25 MPa, inlet air temperature of 120℃, and outlet air temperature of 65℃) to obtain pretreated metronidazole.

[0052] S200: Add pretreated metronidazole, 18 parts corn starch, 14 parts sucrose and 4.5 parts sodium carboxymethyl starch to a high-speed mixing granulator. Mix for 10 minutes, then add 28 parts binder and continue mixing for 10 minutes. Transfer to a gyratory pellet mill (18-mesh nylon screen) for granulation. Dry at 45°C for 35 minutes. Granulate in a gyratory pellet mill (16-mesh nylon screen) to obtain the core material.

[0053] S300: Add the core material, 6.5 parts of sodium carboxymethyl starch and 1.2 parts of magnesium stearate to a three-dimensional motion mixer, mix for 35 minutes, and then compress the mixture into tablets using a rotary tablet press (the speed of the tablet press is 15 rpm) to obtain metronidazole tablets.

[0054] The metronidazole tablets prepared in this embodiment comprise the following raw materials in parts by weight: 100 parts metronidazole, 18 parts corn starch, 14 parts sucrose, 11 parts sodium carboxymethyl starch (4.5 parts + 6.5 parts), 28 parts binder, and 1.2 parts magnesium stearate. The mass ratio of sodium carboxymethyl starch in S200 to sodium carboxymethyl starch in S300 is 1:1.44.

[0055] Example 5 This embodiment provides a method for preparing metronidazole tablets, similar to Example 1, except that in step S100, the 65°C warm water is replaced with room temperature water. The remaining steps and conditions are the same as in Example 1 and will not be repeated here.

[0056] The raw materials and proportions of metronidazole tablets are the same as in Example 1, and will not be repeated here.

[0057] Comparative Example 1 This comparative example provides a method for preparing metronidazole tablets, similar to Example 1, except that the amount of sodium carboxymethyl starch in S200 is replaced with 7.5 parts, and the amount of sodium carboxymethyl starch in S300 is replaced with 5 parts, i.e., the mass ratio of sodium carboxymethyl starch in S200 to sodium carboxymethyl starch in S300 is 1.5:1. The remaining steps and conditions are the same as in Example 1 and will not be repeated.

[0058] The components and proportions of metronidazole tablets are the same as in Example 1, and will not be repeated here.

[0059] Comparative Example 2 This comparative example provides a method for preparing metronidazole tablets, similar to Example 1, except that the amount of sodium carboxymethyl starch in step S200 is replaced with 12.5 parts, and sodium carboxymethyl starch is not added in step S300, meaning that sodium carboxymethyl starch is used entirely as an internal excipient. The remaining steps and conditions are the same as in Example 1 and will not be repeated here.

[0060] The components and proportions of metronidazole tablets are the same as in Example 1, and will not be repeated here.

[0061] Comparative Example 3 This comparative example provides a metronidazole tablet, whose raw materials and proportions are similar to those in Example 1, except that sodium carboxymethyl starch is not added in S200, and the amount of sodium carboxymethyl starch in S300 is replaced with 12.5 parts, that is, all sodium carboxymethyl starch is used as an excipient. The remaining steps and conditions are the same as in Example 1, and will not be repeated here.

[0062] The components and proportions of metronidazole tablets are the same as in Example 1, and will not be repeated here.

[0063] Comparative Example 4 This comparative example provides a method for preparing metronidazole tablets, similar to Example 1, except that in step S100, the metronidazole is not spray-dried, but only passed through a 120-mesh sieve. The remaining steps and conditions are the same as in Example 1 and will not be repeated here.

[0064] The raw materials and proportions of metronidazole tablets are the same as in Example 1, and will not be repeated here.

[0065] Verification test The metronidazole tablets provided in Examples 1-5 and Comparative Examples 1-4 were used as test samples for relevant performance tests, and the results are shown in Tables 1-3.

[0066] Friability: Tested according to pharmacopoeia standards, the weight loss shall not exceed 1%, and no broken, cracked or pulverized pieces shall be detected.

[0067] Dissolution: Metronidazole tablets manufactured by Famar Health Care Services Madrid, SAU were used as the reference formulation. In vitro dissolution profiles were determined in hydrochloric acid solution (pH 1.0), buffer solution (pH 4.0), buffer solution (pH 6.8), and water. The specific method followed the Dissolution and Release Determination Method (General Rule 0931, Method II). Sampling time points were 5 min, 15 min, 30 min, 45 min, 60 min, 90 min, and 120 min. The dissolution medium volume was 500 mL, and the rotation speed was 75 rpm.

[0068] Instruments: Ultraviolet spectrophotometer and dissolution tester.

[0069] Accelerated test: The sample was placed at 40℃±2℃ and RH=75%±5% for 6 months, and samples were taken at the end of the 0th and 6th months to determine its properties, related substances, dissolution curves, etc.

[0070] Table 1. Physical property test results of metronidazole tablets in the examples and comparative examples.

[0071] Table 2. Dissolution and stability test results of metronidazole tablets in the examples and comparative examples.

[0072] Table 3. Results of tests on the properties and impurities of metronidazole tablets in the examples and comparative examples.

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing metronidazole tablets, characterized in that, Includes the following steps: S1. Metronidazole is micronized to obtain pretreated metronidazole; S2. The pretreated metronidazole, corn starch, sucrose, sodium carboxymethyl starch and binder are mixed, granulated, dried and sized to obtain the core material; S3. Mix the core material, sodium carboxymethyl starch and magnesium stearate, compress the mixture into tablets, and obtain metronidazole tablets. The amount of sodium carboxymethyl starch used in S2 is lower than that used in S3.

2. The method for preparing metronidazole tablets as described in claim 1, characterized in that, The mass ratio of sodium carboxymethyl starch in S2 to sodium carboxymethyl starch in S3 is 1:(1.2~2).

3. The method for preparing metronidazole tablets as described in claim 1 or 2, characterized in that, The metronidazole tablets comprise the following raw materials in parts by weight: 100 parts metronidazole, 15 to 25 parts corn starch, 12 to 18 parts sucrose, 10 to 15 parts sodium carboxymethyl starch, 25 to 35 parts binder, and 1 to 2 parts magnesium stearate.

4. The method for preparing metronidazole tablets as described in claim 3, characterized in that, The metronidazole tablets comprise the following raw materials in parts by weight: 100 parts metronidazole, 18 to 22 parts corn starch, 14 to 16 parts sucrose, 11 to 14 parts sodium carboxymethyl starch, 28 to 32 parts binder, and 1.2 to 1.8 parts magnesium stearate.

5. The method for preparing metronidazole tablets as described in claim 1, characterized in that, In S1, the micronization process includes spray drying or air jet milling.

6. The method for preparing metronidazole tablets as described in claim 5, characterized in that, In S1, during the spray drying process, the metronidazole is prepared into a 15wt%~20wt% metronidazole solution using an alcohol solvent; In S1, the feed rate of the spray dryer is 8 mL / min to 12 mL / min, the atomizing pressure is 0.25 MPa to 0.35 MPa, the inlet air temperature is 110℃ to 120℃, and the outlet air temperature is 55℃ to 65℃.

7. The method for preparing metronidazole tablets as described in claim 1, characterized in that, In S2, the method for preparing the adhesive includes the following steps: Corn starch and ethanol are mixed, and water at 80℃~100℃ is added. The mixture is stirred until homogeneous to obtain the adhesive.

8. The method for preparing metronidazole tablets as described in claim 7, characterized in that, In S2, the mass ratio of corn starch, ethanol and water in the adhesive is 1:(5.5~6.5):(2.5~3.5).

9. The method for preparing metronidazole tablets as described in claim 1, characterized in that, In step S2, the drying temperature is 45℃~55℃ and the drying time is 25min~35min.

10. A metronidazole tablet, characterized in that, The metronidazole tablets are prepared by the method described in any one of claims 1 to 9.

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